Straight to voicemail outside business hours?

I need to change the voicemail behavior of a particular extension. When someone calls outside of business hours (9:00 AM to 5:00 PM on weekdays, in my timezone), it should immediately play a special “we’re not in right now, please call back during work hours” recording and go directly to voicemail without ringing. How can I do this?

See time dependent context examples in extensions.conf.sample

Were this Switchvox (let’s pretend?), it comes loaded with a time frame condition for M-F, 5p-9a, S-S, called “Outside Business Hours.” For the extension in question, you’d go to Features>Call Rules>Unanswered Calls, and you’d create a new call rule set, e.g.:
Send my calls to vmail when I want

You’d pick the Outside Business Hours time frame, and you’d let it happen for any presence setting for the user.

Then, it’ll let you choose actions for the rule set, and there’s a button for “Send to Voicemail.”

You can pick the type of calls (Direct, Queue, All), and then you’d set the number of rings (Immediately, for your case).

Then, back in rule sets, make sure this rule is in the list before the Default Standard rule.